C13 or C-13 may refer to:
==Science and technology== IEC 60320 C13, a polarised, three pole plug used in electric power cables Caterpillar C13 Engine, an engine by Caterpillar Inc. Caldwell 13 (NGC 457, the Owl Cluster or ET Cluster), an open star cluster in the constellation Cassiopeia Carbon-13 (13C), a natural stable isotope of carbon Malignant neoplasm of hypopharynx (ICD-10 code), a head and neck cancer Tridecylic acid, a saturated fatty acid
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).